The teachers strike in Chicago, the third largest public school district in the country with some 350,000 students, is about more than money.

Teacher Jillian Connolly helps her daughter, Mary, study math problems while picketing outside of the William H.Wells Community High School in Chicago. (Scott Olson/GETTY IMAGES)

In fact, Karen Lewis, the head of the teachers union, said the two sides were close to agreement on financial matters, but other issues remain outstanding.

While no other teachers union has gone on strike in solidarity, they will be watching to see how this turns out.

More than 26,000 teachers and other unionized school personnel went on strike Monday for the first time in 25 years after the Chicago Teachers Union could not reach a contract agreement with Emanuel and the school district’s leadership.

In July, the two sides had reached an interim agreement on a longer school day, about 90 more minutes a day for elementary school students, who had the shortest day of any big city in the country. The pact called for the hiring of new teachers, but how they would be hired has become a sticking point: by seniority from a pool of laid-off teachers, as the union wants, or by principal discretion, as Emanuel wants.

There are a number of key issues on the table, including:

* Standardized tests and teacher assessment. This is one of the biggest issues in public school reform. A number of states have passed laws — including Illinois — that require teacher evaluations to be based in some large measure on their students standardized test scores. Assessment experts have said repeatedly this is a bad idea — including a group of Illinois researchers and academics who sent an open letter last March to Emanuel school officials warning against implementing a teacher evaluation system based on standardized test scores. But Emanuel is insisting anyway, and in fact wants to the scores to count for more than the state law says.

* Merit pay: This is another big issue in school reform. Emanuel is one of a number of reformers trying to institute a pay system that rewards teachers financially for excellence, which is determined mostly by standardized test scores. Merit pay systems have been tried over the years and have never worked well for teachers for various reasons. Emanuel already unveiled a merit pay system for principals that includes the use of test scores to assess how well a principal is doing.

* Charter schools and teacher placement: Emanuel wants to expand the number of public charter schools, in which some 50,000 Chicago students now attend. Most of the city’s charter schools have no unions and the union is worried that with declining student population as well as poor academic performance, many traditional public schools will be closed and unionized teachers will lose their jobs. The charter schools overall have a mixed academic record, but Emanuel, as well as school reformers in other cities, look on them as one of the things that will improve public education. Critics don’t agree.

* Salaries: Emanuel promised a 4 percent pay raise to teachers last year but dropped that to 2 percent a year for four years because of the district’s dire financial situation. The school district negotiators raised the offer to 3 percent a year over four years in a new offer made to the union Sunday, Reuters said. How much do Chicago teachers earn now? More than teachers in Los Angeles, but a little less than in New York City with a mean of $61,790 annually for a primary school teacher to $69,470 for high school, Reuters reported. Chicago Public schools say the average teacher makes $76,000.

* Underfunded pension fund: Chicago has the most underfunded state pension system in the nation, according to Reuters, at a time when many teachers are retiring